The present investigation assessed the corrosion performance of 14 different Zn and Al sacrificial coating system configurations based on several different accelerated corrosion testing techniques. The coatings systems tested, which incorporated conversion coating layers, primers, and topcoats, were exposed in a marine atmosphere, two different accelerated cabinet tests (SAE J2334 and ASTM B117), and a constant immersion exposure to artificial seawater. Visual observations and electrochemical measurements (including electrochemical impedance spectroscopy [EIS]) were made as a function of exposure time. The results of these tests were used to compare the corrosion protection abilities of the coating systems based on barrier protection and defect protection. Impedance results were found to be useful for assessing barrier protection while scribe damage allowed for defect protection comparisons. In addition, the testing techniques were compared to correlate results and provide an overall ranking of corrosion protection performance for each coating system.

Subject
Test methods, Barriers, Coating performance, Zinc rich coatings, Top coats, Impedance, Constants, Steel, Immersion, Coating defects, Corrosion protection, Barrier coatings, Coating systems
Keywords:
cabinet tests, constant immersion, electrochemical impedance spectroscopy, galvanized steel, marine atmospheric exposure, organic topcoats, sacrificial coatings, thermal spray
NACE International
2007
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